It is known to dissolve the cellulose in systems constituted by organic solvents and other substances which may react with cellulose, and systems of this kind are described in the literature; however they have a purely academic interest since they are not adapted, as far as is known up to now, for carrying out industrial processes.
More recently it has been proposed to use the system constituted by paraformaldehyde or formaldehyde and DMSO. However it is not easy to obtain regenerated cellulose formed bodies from such solutions especially in industrial operation. The most interesting formed bodies are regenerated cellulose filaments and films, which must be prepared through the steps of coagulation, cellulose regeneration and drawing.
In U.S. Pat. No. 4,022,631 a system is described and claimed for coagulating and regenerating the cellulose from said solutions, which consists in employing as coagulating bath an aqueous solution which is alkaline because of the presence of ammonium or amino compounds or alkaline sulphites or thiosulphates, in particular aqueous ammonia. Although said process permits to form regenerated cellulose bodies, still it is not satisfactory both as concerns its industrial practicability and as to the characteristics of the products obtained.